The present invention relates to a one-way ratchet mechanism and, more particularly, to an improved structure of one-way ratchet mechanism adapted for use with a flywheel in a stationary bicycle.
FIG. 1 shows a conventional stationary bicycle. This structure of stationary bicycle comprises a frame, a saddle, a handle, a counter, a flywheel, a one-way ratchet mechanism, and a transmission shaft. As illustrated in FIGS. 2 and 3, the flywheel comprises a hub defining a mounting chamber and a bearing chamber in the mounting chamber. The one-way ratchet mechanism is received in the mounting chamber of the hub and mounted on the transmission shaft, which is supported in an axle bearing in the bearing chamber. When the user pedals the pedals to turn the transmission belt forwards, the transmission shaft is driven to rotate the one-way ratchet mechanism and the flywheel. One the contrary, when the user pedals the pedals in the reversed direction, the needle rollers in the ratchet wheel of the ratchet mechanism run idle, and the ratchet wheel does no work, and therefore the flywheel is immovable.
According to the aforesaid ratchet mechanism, the ratchet wheel is made of metal by stamping, and must be processed through a surface processing process and then treated with a heat treatment after stamping. This complicated fabrication method greatly increases the cost of the ratchet mechanism.
The present invention has been accomplished to provide a one-way ratchet mechanism, which eliminates the aforesaid drawback. According to one aspect of the present invention, the one-way ratchet mechanism comprises a ratchet wheel fastened to a hub of a flywheel, the ratchet wheel having a center axle hole, which receives a transmission shaft, a plurality of inside notches equiangularly spaced around the center axle hole, and a plurality of positioning grooves respectively disposed at one end of each inside notch, a plurality of constraint plates respectively fitted into the positioning grooves and defining with the transmission shaft a respective wedge-like constraint space, a plurality of springs respectively mounted in the inside notches at one end, and a plurality of needle rollers respectively supported on the springs and moved between two ends of each wedge-like constraint space defined between the constraint plates and the transmission shaft to control one-way rotation of the ratchet wheel upon rotation of the transmission shaft. According to another aspect of the present invention, the ratchet wheel is injection-molded from hard plastics, aluminum, or tin, therefore the manufacturing cost of the ratchet wheel is low. According to another aspect of the present invention, the constraint plates are made of metal to protect the ratchet wheel against friction. Because the fabrication and installation of the constraint plates are easy, the one-way ratchet mechanism of the present invention achieves high economic effect and practical value.